1. Field of the Invention
This invention relates to an image display device to which a principle of a fluorescent display device is applied, and more particularly to an image display device including first control electrode means comprising a plurality of control electrodes arranged in parallel to one another and second control electrode means comprising a plurality of control electrodes arranged in parallel to one another and in a direction across the first control electrode means wherein each pair of the control electrode of the first control electrode means and each pair of the control electrodes of the second control electrode means are selectively simultaneously driven for display.
2. Description of the Prior Art
A fluorescent display device generally includes a phosphordeposited anode acting as a luminous section, a cathode acting as an electron emitting source, a control electrode for accelerating and controlling electrons emitted from the cathodes, and a casing which receives the above-described electrodes therein and evacuated to high vacuum. A conventional image display device which utilizes a principle of the fluorescent display device constructed as described above and is adapted to carry out matrix display is classified into two types.
One of the two types is constructed in such a manner that a plurality of strip-like anodes arranged in parallel to one another and a plurality of strip-like mesh-like control electrodes arranged in parallel to one another above the strip-like anodes and in a direction across the anodes cooperate together to constitute a matrix, and a scan drive signal is supplied to the mesh-like control electrodes and a display input signal is supplied to the strip-like anodes in synchronism with supply of the scan drive signal, resulting in luminous display.
The other type image display device is constructed as disclosed in Japanese Patent Application Laying-Open Publication No. 59542/1983. More specifically, a plurality of linear control electrodes are arranged in parallel to one another in each of X and Y directions. Positive voltage is constantly applied to phosphor-deposited anodes, and a scan drive signal is supplied to the respective pairs of adjacent control electrodes in the X direction in order and a display drive signal is supplied to the respective pairs of adjacent control electrodes in the Y direction. This causes any desired areas on the anode to be selected as picture cells, resulting in luminous display.
In the former image display device, a decrease in an interval between adjacent picture cells which is necessary to cause the device to exhibit luminous display of high resolution requires to reduce an interval between adjacent mesh-like control electrodes. However, this renders manufacturing of the device highly troublesome and difficult. Also, the device fails to form a distinct image because electrons which leak through a gap between the mesh-like control electrodes impinge on a phosphor layer which is not desired to exhibit luminous display to lead to leakage luminance. In order to avoid such a problem, it is proposed to cover the gap with an insulating material. Unfortunately, this renders manufacturing of the device further troublesome.
The latter image display device is proposed in order to solve the above-noted problems of the former device. More particularly, a decrease in an interval between picture cells is accomplished by arranging a plurality of the linear control electrodes in parallel to one another in each of the X and Y directions, to thereby prevent the above-noted leakage luminance and facilitate manufacturing of the device. However, it was found that the image display device exhibits an important problem in selection of the picture cells at the time of driving.
The problem will be more detailedly described with reference to FIG. 13 which schematically shows a structure of the image display device.
A plurality of the linear control electrodes arranged in parallel to one another in the X direction or a lateral direction in FIG. 13 are connected to a scan drive circuit connected to a timing control circuit. A plurality of the linear control electrodes arranged in parallel to one another in the Y direction or a vertical direction in FIG. 13 are connected to a display drive circuit connected to the timing control circuit. To the respective pairs of each adjacent two such linear control electrodes in the X direction or a horizontal direction in FIG. 13 is applied the same positive voltage from the scan drive circuit in turn. In synchronism with the application, the display drive circuit supplies a signal corresponding to a display input signal to the linear control electrodes in the Y direction. For example, when it is desired to cause picture cells A, B and D to emit light, it is required that the scan drive circuit simultaneously drives linear control electrodes 1 to 6 at the same positive voltage while the scan drive circuit selectively drives linear control electrodes 7 and 8 at the same positive voltage. However, at this time, linear control electrodes on both sides of a picture cell C which is not desired to emit light are concurrently kept at positive voltage, resulting in the picture cell C undesirably carrying out light emission.